1、Designation: D2807 93 (Reapproved 2015)D2807 17Standard Test Method forChromic Oxide in Leather (Perchloric Acid Oxidation)1This standard is issued under the fixed designation D2807; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method cov
3、ers the determination of chromic oxide in leathers that have been partly or completely tanned withchromium compounds. In general the samples will contain between 1 and 5 % chromium, calculated as chromic oxide.1.2 The values stated in SI units are to be regarded as standard. No other units of measur
4、ement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimita
5、tions prior to use. See Section 7 for specific safety hazards.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations
6、issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D2617 Test Method for Total Ash in LeatherD2813 Practice for Sampling Leather for Physical and Chemical TestsE180D2868 Practice for Determining the Precision of ASTM Methods f
7、or Analysis and Testing of Industrial and SpecialtyChemicalsTest Method for Nitrogen Content (Kjeldahl) and Hide Substance Content of Leather, Wet Blue and Wet White(Withdrawn 2009)D3495 Test Method for Hexane Extraction of LeatherD3790 Test Method for Volatile Matter (Moisture) of Leather by Oven D
8、rying3. Summary of Test Method3.1 The perchloric acid method is applied to the ash obtained in Test Method D2617. In the acid digestion, any remainingorganic matter is destroyed and the chromium oxidized to the hexavalent state. On dilution, the chromium is titrated volumetricallywith thiosulfate or
9、 ferrous salt. The perchloric acid method requires less manipulation than procedures based on fusion of the ash,but care must be taken because of potential hazards in the use of this reagent. The perchloric acid method also tends to give lowresults.4. Significance and Use4.1 The procedure described
10、is specific for chromium in leather. Vanadium is the only common interfering element and this israrely present in quantity. The precision and accuracy of the methods are usually at least as good as the sampling of the leatheritself.4.2 The chromium content of leather relates to the degree of tannage
11、 obtained, and hence may be a matter for specification inthe purchase of leather. The procedure described provides adequate accuracy for this purpose.1 This test method is under the jurisdiction of ASTM Committee D31 on Leather and is the direct responsibility of Subcommittee D31.06 on Chemical Anal
12、ysis This testmethod was developed in cooperation with the American Leather Chemists Assn.Current edition approved Sept. 1, 2015April 1, 2017. Published October 2015May 2017. Originally approved in 1969. Last previous edition approved in 20092015 asD2807 93 (2009)(2015).1. DOI: 10.1520/D2807-93R15.1
13、0.1520/D2807-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is
14、intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the c
15、urrent versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Apparatus5.1 Potentiometric Titration EquipmentThis is required in an alternative method f
16、or titrating chromium (Cr6+) with ferrousammonium sulfate solution. The equipment consists of:5.1.1 Stirrer.5.1.2 Calomel and Platinum Electrodes.5.1.3 PotentiometerA variety of instruments is satisfactory.3 The most convenient common feature of these instruments is anull-point device (either a cath
17、ode-ray electron tube or galvanometer) that will signal the abrupt change occurring in the potentialwhen the end point is reached.5.1.4 In carrying out the titration, the electrodes are immersed in the sample, the solution agitated by the stirrer, and the potentialbalanced with the galvanometer or c
18、athode-ray tube. Titrant is added dropwise until a sharp permanent change in potential occurs.5.2 In carrying out the titration, the electrodes are immersed in the sample, the solution agitated by the stirrer, and the potentialbalanced with the galvanometer or cathode-ray tube. Titrant is added drop
19、wise until a sharp permanent change in potentialoccurs.Perchloric Acid Hood.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to specifications of the Committee on Analytical Reagents of the
20、American Chemical Society, where suchspecifications are available.4 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening the accuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, reference
21、 to water shall be understood to mean distilled water water, deionizedwater, or water of equal purity.6.3 Ferrous Ammonium Sulfate, Standard Solution (0.1 N)Dissolve 39.21 g of ferrous ammonium sulfate(Fe(NH4)2(SO4)26H2O) in water, add 25 mL of H2SO4, anddilute and dilute to 1 L.6.3.1 Standardizatio
22、nDry potassium dichromate (K2Cr2O7) in an oven at 130C 130 C for 2 h and cool in a desiccator.Weighinto a 250-mL glass-stoppered Erlenmeyer flask about 0.200 g of K2Cr2O7 to an accuracy of 0.0001 g. A beaker is preferred ifpotentiometric titration is used. Dissolve in 75 to 100 mL of water, add 20 m
23、L of sulfuric acid (H2SO4, 1+1) and titrate with theferrous ammonium sulfate solution to be standardized. Determine the end point either potentiometrically, or with 1,10-phenanthroline ferrous sulfate solution, 0.025 M,5 as indicator. The potentiometric end point is marked by a sharp decrease inoxid
24、ation potential. The indicator end point is from blue-green to a red-brown. It is preferable not to add the indicator until theend point is approaching, as evidenced by the disappearance of a yellowish-green color and a gradual change to blue-green.6.3.2 The titer of the ferrous ammonium sulfate sol
25、ution decreases slowly because of oxidation of ferrous iron. This change maybe retarded by storing the solution in a dark bottle and by adding a few pieces of mossy tin to the solution. However, the solutionshould be standardized daily whenever samples are being analyzed. Calculate the normality of
26、the ferrous ammonium sulfatesolutions as follows:Normality5A/0.049033B! (1)where:A = grams of K2Cr2O7 used, andB = millilitres required for titration.6.4 Nitric Acid (sp gr 1.42)Concentrated nitric acid (HNO3).6.5 Perchloric Acid (60 percent )%)70 or 72 % perchloric acid (HClO4) may be substituted b
27、ut storage is somewhat morehazardous.6.6 1,10-Phenanthroline-Ferrous Sulfate Solution (0.025 M).56.7 Phosphoric Acid (40 % )(40 %)Dilute 45 mL of 85 % phosphoric acid (H3PO4) with water to 100 mL.6.8 Potassium Iodide Solution (10 %)Dissolve 10 g of potassium iodide (KI) in 100 mL of water.6.9 Sodium
28、 Thiosulfate, Standard Solution (0.1 N)Dissolve 24.85 g of sodium thiosulfate (Na2S2O35H2O) in previouslyboiled water, add 1 g of sodium carbonate (Na2CO3), and dilute to 1 L.6.9.1 StandardizationDry potassium dichromate (K2Cr2O7) in an oven at 130C 130 C for 2 h and cool in a desiccator.Weighinto a
29、 250-mLglass-stoppered Erlenmeyer flask about 0.200 g of K2Cr2O7 to an accuracy of 0.0001 g. Dissolve in 50 mLof water;3 Satisfactory equipment include, among others the following: the Kelley, Serfass, and Fisher tritrimeters, Leeds chromic oxide; perchloric acid oxidationASTM International takes no
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33、ess shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone),
34、610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ The last approved version of this histori
35、cal standard is referenced on www.astm.org.7 Acceptable procedures are published in Journal of the American Leather Chemists Association, JALCA, Vol 51, 1956, p. 497; or Offcial Methods of Analysis, Am.Leather Chemists Assn., available through the Office of Secretary-Treasurer, Texas Tech University, P.O. Box 45300, Lubbock, TX 79409; or see Practice D2813.9 The actual data upon which the results are based are reported in Journal, American Leather Chemists Assn. JALCA, Vol 54, 1959, p. 2.D2807 175
